Method and apparatus for determining a data rate in a high rate packet data wireless communications system

ABSTRACT

In a wireless communication system a method for combination transmission of packet data and low delay data. In one embodiment a parallel signaling channel provides a message to receivers indicating a target recipient of packet data. The message also identifies the transmission channels used for packet data transmissions. Each receiver may then selectively decode only packets where the message identifies the receiver as a target recipient. The data packets stored in a buffer are ignored if the target recipient is another mobile unit. In one embodiment, the message is sent concurrently with the data packet on a parallel channel. In one embodiment, the message is punctured into the high rate packet data transmission.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present Application for patent is a Continuation and claims priorityto patent application Ser. No. 09/697,372 entitled “Method and Apparatusfor Determining a Data Rate in a High Rate Packet Data WirelessCommunications System” filed Oct. 25, 2000, now U.S. Patent No.6,973,098, and assigned to the assignee hereof and hereby expresslyincorporated by reference herein.

REFERENCE TO RELATED CO-PENDING APPLICATIONS FOR PATENT

The present invention related to the following U.S. Application forpatent:

U.S. Patent Application No. 08/963,386 entitled “METHOD AND APPARATUSFOR HIGH RATE PACKET DATA TRANSMISSION,” filed on Nov. 3, 1997, now U.S.Pat. No. 6,574,211, issued Jun. 3, 2003 to Padovani et al., and assignedto the assignee hereof which is hereby expressly incorporated byreference herein;

and to:

U.S. Patent Application No. 09/697,375, filed Oct. 25, 2000, now U.S.Patent No. 7,068,683, entitled METHOD AND APPARATUS FOR HIGH RATE PACKETDATA AND LOW DELAY DATA TRANSMISSIONS, and assigned to the assigneehereof.

FIELD

The present invention relates to wireless data communication. Moreparticularly, the present invention relates to a novel and improvedmethod and apparatus for high speed packet data and low delay datatransmissions in a wireless communication system.

BACKGROUND

Increasing demand for wireless data transmission and the expansion ofservices available via wireless communication technology has led to thedevelopment of specific data services. One such service is referred toas High Data Rate (HDR). An exemplary HDR type system is proposed in“TL80-54421-1 HDR Air Interface Specification”referred to as “the HAIspecification.” HDR generally provides an efficient method oftransmitting packets of data in a wireless communication system. Adifficulty arises in applications requiring both voice and packet dataservices. Voice systems are considered low delay data systems, as thevoice communications are interactive and therefore processed inreal-time. Other low delay data systems include video, multi-media, andother real-time data systems. HDR systems are not designed for voicecommunications but rather are designed to optimize data transmissions,as the base station in an HDR system circulates through the variousmobile users, sending data to only one mobile user at a time. Thecirculation introduces delay into the transmission process. Such delayis tolerable for data transmission, as the information is not used inreal-time. In contrast, the circulation delay is not acceptable forvoice communications.

There is a need for a combination system for transmitting high speedpacket data information along with low delay data, such as voiceinformation. There is a further need for a method of determining thedata rate for high packet data rate information in such a combinationsystem.

SUMMARY

The disclosed embodiments provide a novel and improved method for highpacket data rate and low delay data transmission in a wirelesscommunication system. In one embodiment, a base station in a wirelesscommunication system first sets up low delay data transmission,effectively as high priority, and then schedules packet data servicesaccording to the available traffic power after satisfying the low delaydata. The packet data service transmits the packet data to one mobileuser at a time. Alternate embodiments may provide packet data tomultiple mobile users at a time, dividing the available power among themultiple users. At a given time, one user is selected as a targetrecipient based on the quality of the channel. The base stationdetermines a ratio of the available power to the pilot channel power andprovides the ratio to the selected mobile user. The ratio is referred toas the “Traffic-to-Pilot” ratio, or “T/P” ratio. The mobile user usesthe ratio to calculate a data rate and sends that information back tothe base station.

In one embodiment, the base station provides a “Broadcast-to-Pilot”ratio, or “B/P” ratio to the mobile user, wherein the ratio considersthe broadcast power, i.e., the total available transmission power, ofthe base station and the pilot power, i.e., the power portion of thebroadcast power used for the pilot channel. The mobile user determines anormalized data rate to request from the base station, wherein thenormalized data rate is a function of the B/P. The normalized data rateis sent to the base station and a decision made as to the appropriatedata rate. The data rate selection is then sent to the mobile user.

In an exemplary embodiment, a parallel signaling channel is used toprovide the T/P ratio information to the mobile user. The parallelsignaling channel may be implemented using a separate carrier frequency,or by any of a variety of methods for generating a separate channel.

According to another embodiment, the T/P ratio is provided via thepacket data traffic channel, wherein the T/P ratio is included in theheader of a packet of data, or is provided continuously along with thepacket data.

Alternate embodiments may implement another metric for estimating a SNRof the traffic channel based on the SNR of the pilot channel, whereinthe metric is provided to the mobile user for determination of a datarate. The mobile user requests transmissions at or below the determineddata rate.

In one aspect a wireless communication apparatus includes a firstprocessor operative to receive a first indicator, the first indicatorcorresponding to available packet data transmission power; and acorrelation unit operative to determine a packet data transmission rateindicator as a function of the first indicator and a received pilotsignal strength.

In another aspect, in a wireless communication system, the systemoperative for transmitting packet data and low delay data, the systemhaving a total available transmit power, a method includes establishingat least one low delay communication link using a first power;determining available packet data traffic power as a function of thetotal available transmit power and the first power; determining a packetdata rate based on the available packet data traffic power.

In still another aspect, a wireless communication apparatus includes afirst processor operative to receive a first indicator, the firstindicator corresponding to a ratio of available traffic-to-pilot signalstrength; a measurement unit operative to receive a pilot signal anddetermine a pilot signal-to-noise ratio of a pilot signal; a summationnode coupled to the measurement unit and the first processor, thesummation node operative to adjust the signal-to-noise ratio by thefirst indicator to form a traffic signal-to-noise ratio; and acorrelation unit operative to receive the traffic signal-to-noise ratioand determine an associated data rate for transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the presently disclosed methodand apparatus will become more apparent from the detailed descriptionset forth below when taken in conjunction with the drawings in whichlike reference characters identify correspondingly throughout andwherein:

FIG. 1 illustrates in block diagram form one embodiment of a High DataRate (HDR) protocol wireless communication system;

FIG. 2 illustrates a state diagram describing operation of an HDR systemas in FIG. 1;

FIG. 3 illustrates in graphical form usage patterns for multiple packetdata users within an HDR wireless communication system as in FIG. 1;

FIG. 4 illustrates in graphical form power received by a user within anHDR wireless communication system as in FIG. 1;

FIG. 5 illustrates in block diagram form an HDR wireless communicationsystem including low delay data users according to one embodiment;

FIG. 6-8 illustrate in graphical form power received by users in HDRwireless communication systems according to various embodiments;

FIG. 9 illustrates in block diagram from a portion of a receiver in anHDR wireless communication system according to one embodiment;

FIG. 10 illustrates in flow diagram for processing traffic data in awireless communication system implementing a signaling channel accordingto one embodiment; and

FIG. 11 illustrates in flow diagram for determining a data rate fortransmission in a wireless communication system according to oneembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While it is desirable to implement high rate packet data services andlow delay, voice type services in one system, this is a difficult taskdue to the significant differences between voice services and dataservices. Specifically, voice services have stringent and predetermineddelay requirements. Typically, the overall one-way delay of speechframes must be less than 100 msec. In contrast to voice, the data delaycan become a variable parameter used to optimize the efficiency of thedata communication system. As the condition of a channel to a given userwill vary over time, and it is therefore possible to select the bettertimes to transmit packets based on the channel condition.

Another difference between voice and data services involves therequirement of voice services for a fixed and common grade of service(GOS) for all users. For example, in a digital system the GOS requires afixed and equal transmission rate for all users having no delay greaterthan a maximum tolerable value for the frame error rate (FER) of thespeech frames. In contrast, for data services, the GOS is not fixed, butrather may vary from user to user. For data services, the GOS may be aparameter optimized to increase the overall efficiency of the datacommunication system. The GOS of a data communication system istypically defined as the total delay incurred in the transfer of apredetermined amount of data hereinafter referred to as a data packet.

Yet another significant difference between voice services and dataservices is that the former requires a reliable communication linkwhich, in the exemplary CDMA communication system, is provided by softhandoff. Soft handoff results in redundant transmissions from two ormore base stations to improve reliability. However, this additionalreliability is not required for data transmission because the datapackets received in error can be retransmitted. For data services, thetransmit power used to support soft handoff can be more efficiently usedfor transmitting additional data.

In contrast to voice and other low delay data communications, high datarate data communications typically use packet switched techniques ratherthan circuit switched techniques for transmission. The data is groupedinto small batches to which control information is appended as headerand/or tail. The combination of data and control information forms apacket. As packets are transmitted through a system various delays areintroduced, and may even include loss of one or multiple packets and/orone or more portions of a packet. HDR and other packet data systemstypically tolerate time varying delayed packets as well as lost packets.It is possible to exploit the delay tolerance of packet data systems byscheduling transmissions for optimum channel conditions. In oneembodiment, the transmissions to multiple users are scheduled accordingto the quality of each of transmission link. The transmission uses allavailable power to transmit data to one of the multiple users at a time.This introduces a variable delay, as the multiple users may not have apriori knowledge of the target recipient, the scheduling oftransmissions, the data rate, and/or the configuration information,including the modulation technique, the channel encoding, etc. In oneembodiment, rather than have each receiver estimate such information,the receiver requests a data rate and corresponding configuration. Thescheduling is determined by a scheduling algorithm and sent in asynchronization message.

Prior to requesting the data rate, the receiver determines an optimumdata rate, wherein the data rate may be based on available transmissionpower. The data rate is proportional to the transmission power and thequality of the channel. As used herein, a combination system is a systemcapable of handling both low delay data transmissions and packet datatransmission. In a combination system capable of handling voice andpacket data transmissions, the available power, and thus the availabledata rate, varies with time with the voice activity. The receiver doesnot have knowledge of the voice activity of the system in determining adata rate. One example of a combination system is a Wideband CodeDivision Multiple Access, such as the “ANSI J-STD-01 Draft Standard forW-CDMA (Wideband Code Division Multiple Access) Air InterfaceCompatibility Standard for 1.85 to 1.99 GHz PCS Applications” referredto as “W-CDMA.”Other systems include the “TIA/ELIAS-2000 Standards forcdma200 Spread Spectrum Systems” referred to as “the cdma2000 standard,”or other per-user connection systems.

A packet data system 20 is illustrated in FIG. 1 consistent with theprotocols defined by the HAI specification. In the system 20, a basestation 22 communicates with mobile stations 26 through 28. Each mobilestation 26-28 is identified by an index value from 0 to N, N being thetotal number of mobile stations within the system 20. The packet datachannel 24 is illustrated as a multiplexor to illustrate the switchableconnection. The base station 22 may be referred to as an “accessterminal device” for providing connectivity to users (i.e., mobilestation or access terminal), specifically, one user at a time. Note thatan access terminal is typically connected to a computing device, such asa laptop computer, or a personal digital assistant. An access terminalmay even be a cellular telephone with web access capabilities.Similarly, the packet data channel 24 may be referred to as an “accessnetwork” for providing data connectivity between a packet switched datanetwork and the access terminal device. In one example, the base station22 connects mobile stations 26-28 to the Internet.

In a typical HDR system, packet data communications proceed with onelink to the selected recipient, wherein packet data channel 24 schedulesthe various mobile stations 26-28 one at a time. Forward traffic channelrefers to data transmitted from the base station, and reverse trafficchannel refers to data transmitted from the mobile stations 26-28. Thepacket data system 20 schedules users by implementing one link to oneuser at a given time. This is in contrast to low delay data transmissionsystems where multiple links are maintained concurrently. The use of asingle link allows a higher transmission data rate for the selected linkand optimizes transmissions by optimizing the channel condition for atleast one link. Ideally the base station only uses a channel when it isat an optimum condition.

The user(s) of mobile stations 26-28 that expect data service(s) providea forward traffic channel data rate via a Data Rate Control (DRC)channel to the base station 22. The users are scheduled according to thequality of signal received, wherein scheduling also ensures that usersare scheduled according to a fairness criteria. For example, a fairnesscriterion prevents the system from favoring those mobile users proximateto the base station over others that are distant. The requested datarate is based on the quality of signals received at the scheduled user.The ratio of the Carrier-to-Interference (C/I) is measured and used todetermine a data rate for the communication.

FIG. 2 illustrates a state diagram describing operation of the system 20of FIG. 1, such as an HDR system operation consistent with the HAIspecification. The state diagram describes operation with one mobileuser, MSi. At state 30, labeled “INIT,” base station 22 acquires accessto packet data channel 24. During this state initialization includesacquiring a forward pilot channel and synchronizing control. Uponcompletion of the initialization, operation moves to state 32, labeled“IDLE.” In the idle state the connection to a user is closed and thepacket data channel 24 awaits further command to open the connection.When a mobile station, such as MSi, is scheduled, the operation moves tostate 34, labeled “TRANSMIT.” At state 34, the transmission proceedswith MSi, wherein MSi uses the reverse traffic channel, and the basestation 22 uses the forward traffic channel. If the transmission orconnection fails or the transmission is terminated, operation returns toIDLE state 32. A transmission may terminate if another user of mobilestations 26-28 is scheduled. If a new user outside of mobile stations26-28 is scheduled, such as MSj, operation returns to INIT state 30 toestablish that connection. In this way, the system 20 is able toschedule users 26-28 and also users connected through an alternateaccess network.

Scheduling users allows the system 20 to optimize service to mobilestations 26-28 by providing multi-user diversity. An example of theusage patterns associated with three (3) mobile stations MS0, MSi, andMSN within mobile stations 26-28 is illustrated in FIG. 3. The powerreceived in dB at each user is graphed as a function of time. At time t₁MSN receives a strong signal, while MS0 and MSi are not as strong. Attime t₂ MSi receives the strongest signal, and at time t₃ MS0 receivesthe strongest signal. Therefore, the system 20 is able to schedulecommunications with MSN around time t₁, with MSi around time t₂, andwith MS0 around time t₃. The base station 22 determines the schedulingat least in part based on the DRC received from each mobile station26-28.

An exemplary HDR transmission within system 20 is illustrated in FIG. 4.Pilot channel transmissions are interspersed with the packet datachannel. For example, the pilot channel uses all available power fromtime t₀ to t₁, and similarly from time t₂ to t₃. The packet data channeluses all available power from time t₁ to t₂, and from time t₃, etc. Eachmobile station 26-28 calculates a data rate based on the total availablepower as used by the pilot channel. The data rate is proportional to theavailable power. When the packet data system 20 only transmitspacketized data to mobile stations 26-28, the pilot channel accuratelyreflects the calculation of available power. However, when voice andother low delay data services are coupled within one wirelesscommunication system, the calculation becomes more complex.

FIG. 5 illustrates a CDMA wireless communication system 50 according toone embodiment. The base station 52 communicates with multiple mobileusers that may employ services including, but not limited to, low delaydata-only services, such as voice services, low delay data and packetdata services, and/or packet data-only services. The system implements acdma2000 compatible protocol for transmitting packetized data services,which operates concurrently with a low delay data service. At a giventime, the mobile stations 58 and 60 (MS1 and MS2) use only packet dataservices, the mobile station 56 (MS3) uses a packet data service and alow delay data service, and the mobile station 62 (MS4) uses only avoice service. The base station 52 maintains a communication link withMS4 62 via forward and reverse channels 72, and with MS3 56 via forwardand reverse channels 70. For the HDR communications, the base station 52schedules users for data communication via packet data channel 54. HDRcommunication with MS3 56 is illustrated through channel 64, with MS1 58through channel 66, and with MS2 60 through channel 68. Each of thepacket data service users provides data rate information to the basestation 52 on respective DRCs. In one embodiment, the system 50schedules one packetized data link during a given time period. Inalternate embodiments, multiple links may be scheduled concurrently,wherein each of the multiple links uses only a portion of the availablepower.

Operation of the system 50 according to one embodiment is illustratedgraphically in FIG. 6. The pilot channel is provided continuously, as istypical of low delay data systems. The power used by the low delay datachannel varies continuously over time as transmissions are initiated,processed and terminated, and according to the specifics of thecommunications. The packet data channel uses the available power afterthe pilot channel and low delay data services are satisfied. The packetdata channel is also referred to as a Pooled Supplemental Channel(PSCH), including resources of the system available after dedicated andcommon channels are allocated. As illustrated in FIG. 6, dynamicresource allocation involves pooling all unused power and spectrumspreading codes, such as Walsh codes, to form the PSCH. A maximumbroadcast power is available with respect to the PSCH, which may bereferred to as I_(or)max.

According to one embodiment, the PSCH channel format defines parallelsub-channels, each having a unique spectrum spreading code. One frame ofdata is then encoded, interleaved and modulated. The resultant signal isdemultiplexed over the subchannels. At the receiver, the signals aresummed together to rebuild a frame. A variable frame length-encodingscheme provides for longer frames at lower frame rates per slot. Eachencoded packet is sliced into sub-packets, wherein each sub-packet istransmitted via one or multiple slots, providing incremental redundancy.

In contrast to FIG. 4, the addition of low delay data with the HDRtransmissions introduces a variable floor for measuring the availablepower. Specifically, in a packet data-only system as illustrated in FIG.4, all of the spread spectrum codes, such as Walsh codes, are availablefor use on the selected transmission link. When voice or low delay dataservices are added to the packet data services, the number of availablecodes becomes variable, changing with time. As the number of voice orlow delay data services changes, the number of codes available fortransmitting the data changes.

As illustrated in FIG. 6, MS1 is scheduled during the time period fromt₀ to t₁, and MS2 from t₁, to t₂. During the time period from t₂ to t₃,multiple packetized data links are connected, including MS1, MS3 andMS4. During the time period form t₃ to t₄, MS1 is again scheduled alone.As illustrated, throughout the time periods t₀ to t₄, the power consumedby the low delay data channel varies continuously, impacting the poweravailable for packetized data communications. As each mobile stationcalculates a data rate prior to receiving transmissions, a problem mayoccur during a transmission if the available power is reduced without acorresponding change in the data rate. To provide the mobile station(s)56-60 with current information relating to the available power, the basestation 52 determines a ratio of the available power to the pilotchannel power. The ratio is referred to herein as the “traffic-to-pilotratio”, or “T/P ratio.” The base station 52 provides this ratio to thescheduled mobile station(s) 56-60. The mobile station(s) 56-60 use theT/P ratio in conjunction with the SNR of the pilot channel, hereinreferred to as the “pilot SNR,” to determine a data rate. In oneembodiment the pilot SNR is adjusted based on the T/P ratio to calculatea “traffic SNR,” wherein the traffic SNR is correlated to a data rate.The mobile station(s) 56-60 then transmit the data rate back to the basestation 52 as a DRC data rate request.

In one embodiment, the T/P ratio is included in the header of a packetof data or may be punctured or inserted into the high rate packet datachannel between packetized data traffic. As illustrated in FIG. 7, theT/P ratio information is transmitted prior to traffic and provides themobile station(s) 56-60 updated information regarding the availablepower as a result of changes in the low delay data channel. Such changesalso impact the number of codes, such as Walsh codes, available forspreading the information signals. Less power available and fewer codesavailable results in a decreased data rate. For example, in oneembodiment, the packetized data to a given user, or to all users ifmultiple packetized data links are available, is transmitted overchannels corresponding to Walsh codes 16-19 in a CDMA system.

In an exemplary embodiment illustrated in FIG. 8, a parallel signalingchannel is used to provide the T/P ratio information to the mobile user.The parallel signaling channel is a low rate channel carried by aseparate Walsh code. The parallel signaling channel transmits the targetrecipient, the channels used for the traffic, as well as the type ofcoding used. The parallel signaling channel may be implemented using aseparate carrier frequency, or by any of a variety of methods forgenerating a separate channel.

Note that the packet data to a particular user is transmitted on one ormultiple pre-selected channels. For example, in one embodiment of a CDMAwireless communication system, Walsh codes 16 to 19 are assigned to datacommunications. In the exemplary embodiment illustrated in FIG. 8, asignaling message is transmitted on a separate channel having a lowtransmission rate. The signaling message may be sent concurrently withthe data packet. The signaling message indicates the target recipient ofthe data packet, the transmission channels of the data packet, and wellas the coding used. The signaling message may use a separate Walsh codeor may be time multiplexed into the high rate data by puncture orinsertion.

In one embodiment, the signaling message is encoded into a shorter framethan the frame of the data packet, such as the header, allowing thereceiver to decode the signaling message and make processing decision(s)accordingly. The data received that is potentially targeted for thereceiver is buffered awaiting the processing decision(s). For example,if the receiver is not the target recipient of the data, the receivermay discard the buffered data or may discontinue any preprocessing ofdata, such as buffering, etc. If the signaling channel contains no datafor the receiver, the receiver discards the buffer, else, the receiverdecodes the buffered data using the parameters indicated in thesignaling message, reducing any latency of the system.

In one embodiment, the parallel signaling channel is transmitted tomultiple users. As multiple users are able to distinguish between datato the various users, each of the multiple users is also able to receivea common packet(s) of data. In this way, the configuration informationis provided via the signaling message and each user is able to retrieveand decode the packet(s). In one embodiment, a message is broadcast tomultiple users, wherein a group identifier is also broadcast. Mobileusers belonging to the group know the group identifier a priori. Thegroup identifier may be placed in the header information. The groupidentifier may be a unique Walsh code or other means of identifying thegroup. In one embodiment, mobile user(s) may belong to more than onegroup.

FIG. 9 illustrates a portion of a mobile station 80 adapted forpacketized data service within system 50. The T/P ratio information isprovided to a T/P processor 82. The pilot signal is provided to SNRmeasurement unit 84 for calculation of the SNR of the received pilotsignal. The output of the T/P ratio and the pilot SNR are provided tomultiplier 86 to determine traffic SNR. The traffic SNR is then providedto the data rate correlator 88 that performs an adaptive mapping fromthe traffic SNR to an associated data rate. The data rate correlator 88then generates the data rate for transmission via the DRC. The functionsperformed in this portion of the mobile station 80 may be implemented indedicated hardware, software, firmware, or a combination thereof.

The T/P ratio may be transmitted using the parallel signaling channel asillustrated in FIG. 8. As the receiver will determine the data ratebased on the T/P ratio, the signaling message may not include the datarate. The receiver then determines the arrival timing of data based on atransmitted synchronization message. In one embodiment, a separatesignaling message is generated for the timing information. The signalingmessage is transmitted in parallel to the data. In an alternateembodiment, the signaling message(s) is punctured into the data.

FIG. 10 illustrates a method 100 of processing data in a combinationwireless communication system capable of packet data and low delay datatransmissions according to one embodiment. The mobile station(s) receivea traffic frame, which is information received via the traffic channel,at step 102. The traffic frame is buffered at step 104. Buffering allowsthe mobile station(s) to handle the information at a later time withoutlosing transmitted data. For example, data received may be bufferedwhile other processing is performed. Or as applied in the presentembodiment, the buffering delays processing of data until the mobilestation(s) determines the target recipient of the data. Data targetedfor other mobile stations are not processed, but rather are ignoredsaving valuable processing capability. When a mobile station(s)recognizes itself as a target recipient, the buffered data is availablefor retrieval and processing. The buffered data represents the receivedradio frequency samples. Alternate embodiments may determine a data ratefor transmission without buffering information, wherein the datareceived is processed without being first stored in a buffer.

Continuing with FIG. 10, the mobile station(s) decode recipientinformation associated with the traffic frame at step 104. At decisiondiamond 108 the process determines if a given mobile user matches thetarget recipient. If there is no match, the process continues to step110 to discard the buffered traffic frame. Processing then returns tostep 102 to receive the next traffic frame. If the mobile user matchesthe target recipient, then the traffic channel frame is decoded at step112 and the process returns to step 102. The ability to decode a smallportion of the transmission and avoid unnecessary decoding andprocessing increases the efficiency of operation for a mobile user andreduces the power consumption associated therewith.

FIG. 11 illustrates various methods of determining a data rate in acombination wireless communication system according to one embodiment.The mobile station(s) receives signals via traffic and pilot channels atstep 122. The mobile station(s) determines a “pilot SNR” based on thereceived pilot signal at step 124. In the present embodiment, the pilotsignal is transmitted on a unique channel designated for pilottransmission. In alternate embodiments, the pilot signal may bepunctured into one or more other transmissions on one or more otherchannels. In one embodiment, the pilot signal is transmitted at apredetermined frequency different from the frequency of the trafficchannel. For packet data transmissions the base station and each mobilestation determine a data rate for transmission. In one embodiment thebase station determines the data rate and informs the mobile station. Inanother embodiment, the mobile station determines the data rate andinforms the base station. In still another embodiment, the base stationand mobile station negotiate a data rate, wherein each providesinformation to the other. The decision diamond 126 separates the processflow according to where the data rate decision is made. If the mobilestation makes the data rate decision, processing continues to step 136.If the mobile station does not make the data rate decision, processingcontinues to step 128.

In one embodiment, the method for determining a data rate involvesnegotiation of the mobile station and base station. In the negotiations,the mobile station determines a maximum achievable data rate. Themaximum achievable data rate represents a data rate possible if themobile station is the only receiver of the base station. In this case,the total transmit power available from the base station is dedicated tothe mobile station. As illustrated, at step 128 the mobile stationreceives a Broadcast-to-Pilot ratio, or B/P ratio. The broadcast poweris the total transmit power of the base station. The pilot power is thepower consumed for transmission of the pilot signal from the basestation. The mobile station determines a normalized data rate as afunction of the B/P ratio and the pilot SNR at step 130. The normalizeddata rate corresponds to a data rate the mobile user would request ifall of the broadcast power were available for data traffic to the mobileuser and the pilot signal, ignoring other users within a system such assystem 50 of FIG. 5. In other words, the normalized data rate is themaximum achievable data rate. The normalized data rate is thentransmitted to the base station via the Normalized Data Rate Channel(NDRC) at step 132. The base station receives the NDRC from each mobilestation and determines corresponding data rates for each mobile user.The data rate indicator is then transmitted to each mobile station atstep 134. Processing then continues to step 144 and the mobile receivestraffic at the data rate, and finally returns to step 122.

The B/P ratio represents a constant that will typically vary relativelyslowly over time. The base station knows the ratio of total broadcastpower and the power used for the pilot channel. Alternate embodimentsmay implement other indicators of the available power, such as usingother expression(s) of the energy of transmitted signals, the powerspectral density of the signals, etc.

Continuing with FIG. 11, in an alternate method of determining a datarate, the data rate decision is made by the mobile station. For thisembodiment, at step 136 the mobile station receives a Traffic-to-Pilotratio, T/P ratio. At step 138 the mobile station uses the calculatedpilot SNR to generate a “traffic SNR” by adjusting the pilot SNRaccording to the power available for traffic transmissions. In thepresent embodiment the T/P ratio is used to adjust the pilot SNR. Thetraffic SNR then reflects the estimated SNR of the traffic transmissionsusing the available power. The traffic SNR is correlated to a data rateat step 140. The traffic SNR may be correlated to aCarrier-to-Interference (C/I) ratio or other indicator of the quality ofthe channel. In one embodiment a lookup table stores traffic SNRs andassociated data rates. The data rate is then provided as a request tothe base station on the Data Request Channel (DRC) at step 142.Processing then continues to step 144.

In an alternate embodiment, the mobile station estimates the T/P ratiousing the received pilot signal. The received pilot signal provides achannel estimate used for decoding the traffic information. A low passfilter may be used to filter noise components from the received pilotsignal. The filtering provides an estimate of the noise received withthe pilot signal. The T/P ratio is then estimated based on the filteringresults. As an example, consider a system model described by thefollowing:r _(k) ^(t) =√{square root over (T)}cs _(k) +n _(k) ^(t) r _(k) ^(p)=√{square root over (P)}c+n _(k) ^(p) for k=0, 1 . . . , M−1.  (1)

-   -   wherein r_(k) ^(t) and r_(k) ^(p) are the traffic and pilot        signals, respectively, received at a mobile station. The channel        gain, c is complex. The noise associated with the traffic and        pilot are given as n_(k) ^(t) and n_(k) ^(p), respectively. The        lumped power for the pilot and traffic are given as P and T,        respectively. As described T=E_(c) ^(t)G_(t) and P=E_(c)        ^(p)G_(p), wherein E_(c) ^(t) and E_(c) ^(p) represent the        energy per chip for the traffic and pilot channels,        respectively, and wherein G_(t) and G_(p) are the corresponding        processing gains. Note that noises n_(k) ^(t) and n_(k) ^(p) are        considered independent due to the orthogonality between        different code channels, both with zero mean and variance N_(t).        For the above described system model, an estimate of the        traffic-to-pilot ratio is given as:

$\begin{matrix}{R = {\sqrt{\frac{T}{P}}.}} & (2)\end{matrix}$

The Maximum Likelihood (ML) estimate of the traffic-to-pilot ratio maybe found using the following estimate:

$\begin{matrix}{\hat{R} = \frac{\begin{matrix}{{{\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}^{*}r_{k}^{t}}}} \right)^{2} + {\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}r_{k}^{p}}} \right)^{2}\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}}^{2}}} \right)}}} +} \\{{{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}^{*}r_{k}^{t}}}}}^{2} - {{{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}r_{k}^{p}}}}^{2}\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}}^{2}}} \right)}}\end{matrix}}{2\;{{Re}\left\lbrack {\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}^{*}r_{k}^{t}}}} \right)\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}r_{k}^{p}}} \right)^{*}} \right\rbrack}\left( {\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}}^{2}}} \right)}} & (3)\end{matrix}$After some approximation, (3) reduces to:

$\begin{matrix}\begin{matrix}{\hat{R} \approx {{{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}^{*}\frac{r_{k}^{t}}{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}}}}} \times \frac{1}{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}}^{2}}}}} \\{{\approx {{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{s_{k}^{*}\frac{r_{k}^{t}}{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}}}}}},}\end{matrix} & (4)\end{matrix}$wherein the constellation is assumed to have unit averaged power.

The estimates in (3) and (4) may be difficult to evaluate, as the datasequence {s_(k)}, representing the transmitted signal, is included inthe equations. However, these equations suggest that

$\frac{r_{k}^{t}}{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}$is a sufficient statistic that may be used in T/P ratio estimationalgorithm design.

According to one embodiment, an algorithm for estimating the T/P ratiofirst estimates h=√{square root over (P)}c with

$\hat{h} = {\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}$and the noise variance N_(t) from r_(k) ^(p). Next the algorithm definesan estimate of the T/P ratio as:

$\begin{matrix}\begin{matrix}{\hat{R} = \sqrt{{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{\frac{r_{k}^{t}}{h}}^{2}}} - \frac{{\hat{N}}_{t}}{{\hat{h}}^{2}}}} \\{{= \sqrt{{\frac{1}{M}{\sum\limits_{k = 0}^{M - 1}{\frac{r_{k}^{t}}{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}}^{2}}} - \frac{{\hat{N}}_{t}}{{{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}}^{2}}}},}\end{matrix} & (5)\end{matrix}$wherein the estimate of (5) is asymptotically unbiased. Note that anoptimal estimate considers the first moment of the test statistics,while the estimate of (5) intends to estimate the second order moment.While both approaches result in unbiased estimates, the second ordermoment will typically introduce a larger estimation variance. Consideralso that using the first order moment, the required data sequence isunavailable, and the mobile station uses a priori the specific format ofthe constellation.

In another embodiment, a T/P ratio estimation algorithm estimatesh=√{square root over (P)}c with

$\hat{h} = {\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}$and obtains the empirical probability density function (PDF) of

$x_{k} = {\frac{r_{k}^{t}}{\frac{1}{M}{\sum\limits_{m = 0}^{M - 1}r_{m}^{p}}}.}$Note that, for sufficiently large M, x_(k) can be consideredapproximately Gaussian with mean Rs_(k). It is then possible to extractan estimate of R from the PDF of x_(k). At this point there are avariety of ways to estimate R from the PDF of x_(k). Several propertiescan be used in extracting the traffic-to-pilot ratio from the PDF. Forexample, for a high-order modulation such as associated with a high SNR,x_(k)'s are grouped into several clusters. The layout of the centers ofthe clusters is similar to that of the constellation of s_(k). ForM-PAM, M-QAM and M-PSK, the constellation points are equally spaced.Note also that the distribution of each cluster approximately followsthe Gaussian PDF. With source coding, such as compression and/orvocoding, and channel coding the transmitted symbols are equally likely.

The algorithm may continue in the frequency domain or the time domain.For a frequency domain analysis, the points of a constellation may bearranged equally spaced, as are the clusters of the PDF of x_(k),indicating the PDF is periodic. The space, or period, is then determinedby frequency domain analysis. For example, creating a histogram bycalculating the DFT of the PDF function, the algorithm then locates themajor period. R may be calculated based on the major period and theperiod between any two constellation points. For M-QAM, thetwo-dimensional PDF function can be considered as two separateone-dimensional functions. Alternately, the equal spacing property maybe exploited in the time domain. For example, by calculation of theauto-correlation function of the PDF, the position of the firstside-lobe next to zero offset may provide an estimate of the averageperiod between the center of the two adjacent clusters.

In still another embodiment, the N centers of the clusters of the PDFare first located. This method assumes that the estimated centers are{d_(k)} for k=0, 1, . . . , N−1, and the constellation points {a_(k)}for k=0, 1, . . . , N−1, are in a same order. Application of the leastsquare algorithm results in the following estimate of R

$\begin{matrix}{\hat{R} = {\frac{{{Re}\left\lbrack {\frac{1}{N}{\sum\limits_{m}{a_{m}d_{m}^{*}}}} \right\rbrack}}{\frac{1}{N}{\sum\limits_{m}{a_{m}}^{2}}} = {{{Re}\left\lbrack {\frac{1}{N}{\sum\limits_{m}{a_{m}d_{m}^{*}}}} \right\rbrack}}}} & (6)\end{matrix}$Note that the centers for the PDF function may be determined in avariety of ways.

Since the constellation points are equally likely, the method firstfinds the Cumulative Probability Function (CDF) from the PDF. Theclustering is performed by application of a threshold scheme on the CDF.The center of each group is then calculated by averaging within thegroup using a first order moment. In alternate embodiments, techniquessuch as feature extraction used in image processing may be applied,wherein for example, a feature may be a peak or a template based on anapproximation to the Gaussian PDF. Note also that image segmentationtechniques, such as clustering and region growing, provide methods forgrouping the points of the empirical PDF. Comparing (6) and (4)illustrates a similarity between clustering processes and hard-decoding,wherein the actual signal s_(k) in (4) is replaced by the hard-decodedsymbol a_(m) in (6).

In a typical HDR system, such as system 20 illustrated in FIG. 1, onelink is established between the base station at a time. In oneembodiment, a wireless communication system is extended to supportmultiple users at one time. In other words, system 50 of FIG. 5 allowsthe base station 52 to transmit data to multiple data users of mobileunits 56, 58, and 60, concurrently. Note that while four (4) mobileunits are illustrated in FIG. 5, there may be any number of mobile unitswithin system 50 communicating with base station 52. Extension tomultiple users provides for multiple communications via the packet datachannel 54. At a given time, the users supported by the packet datachannel are referred to as “active receivers.” Each active receiverdecodes the signaling message(s) to determine the T/P ratio of thepacket data channel 54. Each active receiver processes the T/P ratiowithout consideration of the potential for other active receiver(s). Thebase station receives data rate requests from each active receiver andallocates power proportionally.

Returning to FIG. 1, in a conventional HDR communication system, muchinformation is known a priori, including but not limited to,constellation information, encoding scheme, channel identification, andpower available for transmission of packet data. Constellationinformation refers to the modulation scheme with which the digital datainformation is modulated onto a carrier for transmission. Modulationschemes include, but are not limited to, Binary Phase-Shift Keying,Quadrature Phase-Shift Keying (QPSK), Quadrature Amplitude Mapping(QAM), etc. The encoding scheme encompasses aspects of coding the sourceinformation into a digital form, including, but not limited to,Turbo-coding, convolutional coding, error coding, such as CyclicRedundancy Check (CRC), rate sets, etc. The receiver via the DRC mayrequest the constellation and encoding information. Channelidentification includes, but is not limited to, spreading codes in aspread spectrum communication system, such as Walsh codes, and mayinclude the carrier frequency. The channel identification may bepredetermined and fixed. The transmission power available for packetdata transmission is typically known, based on the known total transmitpower available and the known pilot signal power.

In a combination, packet data and low delay data, system some of theabove mentioned information is not known a priori, but rather is subjectto variation due to the sharing of the available power and availablechannels with low delay data, such as voice communications. A comparisonis made in the following table.

TABLE 1 Information Available in HDR Systems COMBI- HDR COMBINATIONNATION INFORMATION PACKET DATA T/P SIGNALING ONLY CHANNEL TargetRecipient DECODE packet DECODE packet Message Constellation DRC DRC DRCEncoding DRC DRC DRC Channel(s) FIXED Unknown Message Traffic Power forFIXED T/P Unknown Data

The use of a signaling channel, as illustrated in FIG. 8, provides muchof this information to the receiver. The message identifies the targetrecipient(s) and the channel(s) for the packet data transmission. TheDRC information requests a data rate, specifying the constellation andthe encoding. The provision of the available traffic power indicator,wherein in one embodiment the indicator is a ratio of the availabletraffic power to the pilot signal strength, provides a measure fordetermining the data rate. According to one embodiment implementing aseparate parallel signaling channel, the information related to targetrecipient, constellation, and encoding is transmitted via the trafficchannel and/or DRC, while the information relating to channel(s) andtraffic power for data is transmitted via the parallel signalingchannel.

Application of the embodiments and combinations of embodiments describedhereinabove, allow for combination of packet data with low delay datatransmissions within a wireless communication system. As indicated, thecombination of voice with packet data introduces variables into thetransmission process. The application of a separate signaling channelingprovides information to receivers within a wireless communication systemwithout degrading the quality of the communication. The signalingchannel message may identify target recipient(s) information. Thetransmission of an available traffic indicator to a receiver providesinformation that assists the receiver in determining a data rate torequest from the transmitter. Similarly, when the traffic indicator isused by multiple receivers, wherein each calculates a data ratetherefrom, the transmitter receives information that assists thetransmitter in allocating transmission channels for packet datatransmissions to the multiple receivers.

Thus, a novel and improved method and apparatus for high data ratetransmission in a wireless communication system has been described.While the exemplary embodiment discussed herein describes a CDMA system,various embodiments are applicable to any wireless per-user connectionmethod. To effect efficient communications, the exemplary embodiment isdescribed with respect to HDR, but may also be efficient in applicationto IS-95, W-CDMA, IS-2000, GSM, TDMA, etc.

Those of skill in the art would understand that the data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description are advantageouslyrepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Thevarious illustrative components, blocks, modules, circuits, and stepshave been described generally in terms of their functionality. Whetherthe functionality is implemented as hardware or software depends uponthe particular application and design constraints imposed on the overallsystem. Skilled artisans recognize the interchangeability of hardwareand software under these circumstances, and how best to implement thedescribed functionality for each particular application.

As examples, the various illustrative logical blocks, modules, circuits,and algorithm steps described in connection with the embodimentsdisclosed herein may be implemented or performed with a Digital SignalProcessor (DSP), an Application Specific Integrated Circuit (ASIC), aField Programmable Gate Array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components such as,e.g., registers and First In First Out (FIFO) type, a processorexecuting a set of firmware instructions, any conventional programmablesoftware module and a processor, or any combination thereof designed toperform the functions described herein. The processor may advantageouslybe a microprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine.The software modules could reside in Random Access Memory (RAM), FLASHmemory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM)memory, Electrically Erasable Programmable ROM (EEPROM), registers, harddisk, a removable disk, a Compact Disk-ROM (CD-ROM), or any other formof storage medium known in the art. The processor may reside in an ASIC(not shown). The ASIC may reside in a telephone (not shown). In thealternative, the processor may reside in a telephone. The processor maybe implemented as a combination of a DSP and a microprocessor, or as twomicroprocessors in conjunction with a DSP core, etc.

The previous description of the preferred embodiments is provided toenable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

We claim:
 1. A mobile station comprising: a processor configured to:receive a broadcast-to-pilot ratio from a base station; determine anormalized data rate as a function of the received broadcast-to-pilotratio and a power of a pilot signal received from the base station; anda transmitter configured to transmit the normalized data rate to thebase station.
 2. The mobile station of claim 1, wherein the processor isfurther configured to receive a data rate indicator from the basestation, the date rate indicator based on the transmitted normalizeddate rate.
 3. The mobile station of claim 2, further comprising: areceiver configured to receive traffic from the base station at a daterate indicated by the data rate indicator.
 4. A mobile stationcomprising: means for receiving a broadcast-to-pilot ratio from a basestation; means for determining a normalized data rate as a function ofthe received broadcast-to-pilot ratio and a power of a pilot signalreceived from the base station; and means for transmitting thenormalized data rate to the base station.
 5. The mobile station of claim4 further comprising: means for receiving a data rate indicator from thebase station, the date rate indicator based on the transmittednormalized date rate.
 6. The mobile station of claim 5 furthercomprising: means for receiving traffic from the base station at a daterate indicated by the data rate indicator.
 7. A method of operating amobile station comprising: receiving a broadcast-to-pilot ratio from abase station; determining, by said mobile station, a normalized datarate as a function of the received broadcast-to-pilot ratio and a powerof a pilot signal received from the base station; and transmitting, bysaid mobile station, the normalized data rate to the base station. 8.The method of claim 7 further comprising: receiving a data rateindicator from the base station, the date rate indicator based on thetransmitted normalized date rate.
 9. The method of claim 8 furthercomprising: receiving traffic from the base station at a date rateindicated by the data rate indicator.
 10. A non-transitoryprocessor-readable medium memory having instructions thereon executableby a processor, the instructions comprising: code for receiving abroadcast-to-pilot ratio from a base station; code for determining anormalized data rate as a function of the received broadcast-to-pilotratio and a power of a pilot signal received from the base stations; andcode for transmitting the normalized data rate to the base station. 11.A non-transitory processor-readable medium memory of claim 10 furthercomprising: code for receiving a data rate indicator from the basestation, the date rate indicator based on the transmitted normalizeddate rate.
 12. A non-transitory processor-readable medium memory ofclaim 10 further having comprising: code for receiving traffic from thebase station at a date rate indicated by the data rate indicator.